Antenna device

ABSTRACT

An antenna apparatus in which a combination of rectangular waveguides  9   a  and  10   a  and a combination of rectangular waveguides  9   b  and  10   b  are disposed bilateral symmetrically to each other, and a waveguide orthomode transducer  13  is disposed above a waveguide orthomode transducer  8  is provided. Therefore, the profile of the antenna apparatus can be reduced and the stability of installation of the antenna apparatus can be improved without impairing the electric characteristics of the antenna apparatus. Since the antenna apparatus has a bilateral symmetric structure, it excels in weight balance and offers stable performance from the viewpoint of mechanism.

FIELD OF THE INVENTION

The present invention relates to an antenna apparatus used in, forexample, a VHF band, a UHF band, a microwave band, a millimeter waveband, etc.

BACKGROUND OF THE INVENTION

A prior art antenna apparatus is equipped with a circularly polarizedwave generator and a polarizer, which are mounted on a rotary joint or arotary mechanism, so as to allow integral rotation of a reflector and aprimary radiator (refer to the following non-patent reference 1).

[Non-Patent Reference 1]

Takashi Kitsuregawa, ‘Advanced Technology in Satellite CommunicationAntennas: Electrical & Mechanical Design’, ARTECH HOUSE INC., pp. 232 to235, 1990.

A problem with the prior art antenna apparatus constructed as mentionedabove is that while it can rotate both the reflector and the primaryradiator in a direction of an elevation angle or in a direction of anazimuth angle, the part of the prior art antenna apparatus which isarranged above the rotary mechanism has a very large size and has a highposition, and therefore the prior art antenna apparatus lacks ininstallation stability because the circularly polarized wave generatorand the polarizer are placed on the rotary joint or the rotarymechanism.

The present invention is made in order to solve the above-mentionedproblem, and it is therefore an object of the present invention toprovide an antenna apparatus having a low profile and high installationstability without impairing its electric characteristics.

DISCLOSURE OF THE INVENTION

An antenna apparatus in accordance with the present invention includes afirst rectangular waveguide for propagating a third linearly polarizedwave signal outputted thereto from a second orthomode transducer, asecond rectangular waveguide for propagating a fourth linearly polarizedwave signal outputted thereto from the second orthomode transducer, anda third orthomode transducer for combining the third and fourth linearlypolarized wave signals respectively propagated thereto by the first andthe second rectangular waveguides into a circularly polarized wavesignal, and for outputting the circularly polarized wave signal to aradiator, the first and second rectangular waveguides being disposedbilateral symmetrically to each other and the third orthomode transducerbeing disposed below the second orthomode transducer.

Therefore, the present embodiment offers an advantage of being able toreduce the profile of the antenna apparatus and to improve theinstallation stability without impairing the electric characteristics ofthe antenna apparatus.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side view showing an antenna apparatus according toembodiment 1 of the present invention;

FIG. 2 is a top plan view showing the antenna apparatus of FIG. 1;

FIG. 3 is a side view showing an antenna apparatus according toembodiment 2 of the present invention;

FIG. 4 is a top plan view showing waveguide orthomode transducers 1 and8 of an antenna apparatus according to embodiment 3 of the presentinvention;

FIG. 5 is a perspective diagram showing a waveguide orthomode transducerof FIG. 4;

FIG. 6 is a top plan view showing a waveguide orthomode transducer of anantenna apparatus according to embodiment 4 of the present invention;

FIG. 7 is a perspective diagram showing the waveguide orthomodetransducer of FIG. 6;

FIG. 8 is a side view showing an antenna apparatus according toembodiment 5 of the present invention;

FIG. 9 is a top plan view showing the antenna apparatus of FIG. 8;

FIG. 10 is a block diagram showing an RF module;

FIG. 11 is a block diagram showing an RF module; and

FIG. 12 is a side view showing an antenna apparatus according toembodiment 7 of the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

Hereafter, in order to explain this invention in greater detail, thepreferred embodiments of the present invention will be described withreference to the accompanying drawings.

Embodiment 1

FIG. 1 is a side view showing an antenna apparatus according toembodiment 1 of the present invention, and FIG. 2 is a top plan viewshowing the antenna apparatus of FIG. 1.

In the figure, a waveguide orthomode transducer 1 constitutes a firstorthomode transducer that when receives both a linearly polarized wavesignal L1 (i.e., a first linearly polarized wave signal) via aninput/output terminal P1 and a linearly polarized wave signal (i.e., asecond linearly polarized wave signal) L2 having the same amplitude asthe linearly polarized wave signal L1 via an input/output terminal P2and having a phase difference of 90 degrees with respect to the linearlypolarized wave signal L1, combines the linearly polarized wave signal L1and the linearly polarized wave signal L2 into a composite signal andthen outputs a circularly polarized wave signal C1 that is the compositesignal via an input/output terminal P3.

A rectangular-to-circular waveguide transformer 4 is connected to thewaveguide orthomode transducer 1, and propagates the circularlypolarized wave signal C1 outputted from the input/output terminal P3 ofthe waveguide orthomode transducer 1 to another rectangular-to-circularwaveguide transformer 6. The other rectangular-to-circular waveguidetransformer 6 propagates the circularly polarized wave signal C1propagated thereto by the rectangular-to-circular waveguide transformer4 to a waveguide orthomode transducer 8.

A rectangular waveguide rotary joint 5 is inserted between therectangular-to-circular waveguide transformer 4 and the otherrectangular-to-circular waveguide transformer 6, and constitutes anazimuth rotary member that supports rotation of members (for example, aprimary radiator 14, a main reflector 16, and a subreflector 15), whichare disposed above the rectangular waveguide rotary joint 5, in adirection of an azimuth angle under the control of an azimuth rotarymechanism 7. It is assumed that the rectangular waveguide rotary joint 5is constructed so that a circular-waveguide TE11 mode is defined as apropagation mode. The azimuth rotary mechanism 7 is a mechanical unitfor rotating the rectangular waveguide rotary joint 5 about an azimuthaxis D.

The waveguide orthomode transducer 8 is disposed above the waveguideorthomode transducer 1, and constitutes a second orthomode transducerthat, when receiving the circularly polarized wave signal C1 outputtedthereto from the rectangular-to-circular waveguide transformer 6 via theinput/output terminal P4, separates the circularly polarized wave signalC1 into a linearly polarized wave signal (i.e., a third linearlypolarized wave signal) L3 and a linearly polarized wave signal (i.e., afourth linearly polarized wave signal) L4 having the same amplitude asthe linearly polarized wave signal L3 and having a phase difference of90 degrees with respect to the linearly polarized wave signal L3, andthen outputs the third and fourth linearly polarized wave signals L3 andL4 via input/output terminals P5 and P6, respectively.

A rectangular waveguide 9 a propagates the linearly polarized wavesignal L3 outputted thereto via the input/output terminal P5 of thewaveguide orthomode transducer 8 to another rectangular waveguide 10 a,and the other rectangular waveguide 10 a the propagates the linearlypolarized wave signal L3 to a waveguide orthomode transducer 13. Therectangular waveguides 9 a and 10 a constitute a first rectangularwaveguide.

A rectangular waveguide 9 b propagates the linearly polarized wavesignal L4 outputted thereto via the input/output terminal P6 of thewaveguide orthomode transducer 8 to another rectangular waveguide 10 b,and the other rectangular waveguide 10 b then propagates the linearlypolarized wave signal L4 to a waveguide orthomode transducer 13. Therectangular waveguides 9 b and 10 b constitute a second rectangularwaveguide.

The rectangular waveguides 9 a and 9 b are formed so that they arebilateral symmetric to each other, and the rectangular waveguides 10 aand 10 b are formed so that they are bilateral symmetric to each other.

A rectangular waveguide rotary joint 11 a is inserted between therectangular waveguide 9 a and the rectangular waveguide 10 a, andconstitutes an elevation angle rotary member that supports rotation ofthe waveguide orthomode transducer 13, the primary radiator 14, thesubreflector 15, and the main reflector 16 in a direction of anelevation angle under the control of an elevation angle rotary mechanism12 a. The elevation angle rotary mechanism 12 a is a mechanical unit forrotating the rectangular waveguide rotary joint 11 a around an elevationangle axis E.

Another rectangular waveguide rotary joint 11 b is also inserted betweenthe rectangular waveguide 9 b and the rectangular waveguide 10 b, andconstitutes an elevation angle rotary member that supports rotation ofthe waveguide orthomode transducer 13, the primary radiator 14, thesubreflector 15, and the main reflector 16 in the direction of theelevation angle under the control of an elevation angle rotary mechanism12 b. The elevation angle rotary mechanism 12 b is a mechanical unit forrotating the rectangular waveguide rotary joint 11 b around theelevation angle axis E.

The waveguide orthomode transducer 13 is disposed below the waveguideorthomode transducer 8, and constitutes a third orthomode transducerthat when receiving both the linearly polarized wave signal L3propagated by the rectangular waveguide 10 a via an input/outputterminal P7 and the linearly polarized wave signal L4 propagated by therectangular waveguide 10 b via an input/output terminal P8, combines thelinearly polarized wave signals L3 and L4 into a composite signal, andthen outputs a circularly polarized wave signal C2 which is thecomposite signal via an input/output terminal P9. The primary radiator14 is disposed above the waveguide orthomode transducer 13, and emitsthe circularly polarized wave signal C2 outputted thereto via theinput/output terminal P9 of the waveguide orthomode transducer 13 to thesubreflector 15.

The subreflector 15 is disposed so that its reflecting surface isoriented in a downward direction and reflects the circularly polarizedwave signal C2 emitted from the primary radiator 14 toward the mainreflector 16. The main reflector 16 is disposed so that its reflectingsurface is oriented in an upward direction and emits the circularlypolarized wave signal C2 reflected by the subreflector 15 in the air. Asupporting structure 17 supports the subreflector 15 and the mainreflector 16 so that they are apart from each other and are alignedalong the azimuth axis.

Next, the operation of the antenna apparatus in accordance with thisembodiment of the present invention will be explained.

A case where the antenna apparatus emits a circularly polarized wavesignal C2 toward a target will be explained first.

When receiving both a linearly polarized wave signal L1 via theinput/output terminal P1 and a linearly polarized wave signal L2 havingthe same amplitude as the linearly polarized wave signal L1 via theinput/output terminal P2 and having a phase difference of 90 withrespect to the linearly polarized wave signal L1, the waveguideorthomode transducer 1 combines the linearly polarized wave signals L1and L2 into a composite signal and then outputs a circularly polarizedwave signal C1 that is the composite signal via the input/outputterminal P3.

When receiving the circularly polarized wave signal C1 from theinput/output terminal P3 of the waveguide orthomode transducer 1, therectangular-to-circular waveguide transformer 4 propagates thecircularly polarized wave signal C1 to the rectangular-to-circularwaveguide transformer 6, and the rectangular-to-circular waveguidetransformer 6 then propagates the circularly polarized wave signal C1propagated by the rectangular-to-circular waveguide transformer 4 to thewaveguide orthomode transducer 8.

When receiving the circularly polarized wave signal C1 propagated by therectangular-to-circular waveguide transformer 6 from the input/outputterminal P4, the waveguide orthomode transducer 8 separates thecircularly polarized wave signal C1 into linearly polarized wave signalsL3 and L4, and then outputs the linearly polarized wave signal L3 viathe input/output terminal P5 and outputs the linearly polarized wavesignal L4 having the same amplitude as the linearly polarized wavesignal L3 and having a phase difference of 90 degrees with respect tothe linearly polarized wave signal L3 via the input/output terminal P6.

When receiving the linearly polarized wave signal L3 from theinput/output terminal P5 of the waveguide orthomode transducer 8, therectangular waveguide 9 a propagates the linearly polarized wave signalL3 to the rectangular waveguide 10 a, and the rectangular waveguide 10 athen propagates the linearly polarized wave signal L3 to the waveguideorthomode transducer 13.

On the other hand, when receiving the linearly polarized wave signal L4from the input/output terminal P6 of the waveguide orthomode transducer8, the rectangular waveguide 9 b propagates the linearly polarized wavesignal L4 to the rectangular waveguide 10 b, and the rectangularwaveguide 10 b then propagates the linearly polarized wave signal L4 tothe waveguide orthomode transducer 13.

When receiving both the linearly polarized wave signal L3 propagated bythe rectangular waveguide 10 a via the input/output terminal P7 and thelinearly polarized wave signal L4 propagated by the rectangularwaveguide 10 b via the input/output terminal P8, the waveguide orthomodetransducer 13 combines the linearly polarized wave signals L3 and L4into a composite signal, and then outputs a circularly polarized wavesignal C2 which is the composite signal via the input/output terminalP9.

When receiving the circularly polarized wave signal C2 from theinput/output terminal P9 of the waveguide orthomode transducer 13, theprimary radiator 14 emits the circularly polarized wave signal C2 to thesubreflector 15.

As a result, the circularly polarized wave signal C2 is reflected towardthe main reflector 16 by the subreflector 15, and is further reflectedtoward the air by the main reflector 16.

Although the rectangular waveguide rotary joints 11 a and 11 b rotatethe waveguide orthomode transducer 13, the primary radiator 14, thesubreflector 15, and the main reflector 16 around the elevation angleaxis E under the control of the elevation angle rotary mechanisms 12 aand 12 b, and the rectangular waveguide rotary joint 5 rotates thewaveguide orthomode transducer 8, the rectangular waveguides 9 a, 9 b,10 a, and 10 b, the waveguide orthomode transducer 13, the primaryradiator 14, the subreflector 15, and the main reflector 16 around theazimuth axis D under the control of the azimuth rotary mechanism 7, theamplitude and phase relationship between the linearly polarized wavesignals L3 and L4 inherits the amplitude and phase relationship betweenthe linearly polarized wave signals L1 and L2 because the rectangularwaveguides 9 a and 9 b are formed so that they are bilateral symmetricto each other and the rectangular waveguides 10 a and 10 b are formed sothat they are bilateral symmetric to each other. In other words, thelinearly polarized wave signal L3 and the linearly polarized wave signalL4 are equal in amplitude, and are 90 degrees out of phase with eachother.

Therefore, even if the waveguide orthomode transducer, the primaryradiator, the subreflector, and the main reflector are driven over alarge angle range with respect to the direction of the elevation angle,the good circularly polarized wave state of the circularly polarizedwave signal C2 outputted from the input/output terminal P9 of thewaveguide orthomode transducer 13 can be maintained. The antennaapparatus can thus emit a good-quality circularly polarized wave signalin a wide band.

Since the rectangular waveguide rotary joint 5 is constructed so thatthe circular-waveguide TE11 mode is defined as the propagation mode, itcan drive the waveguide orthomode transducer, the rectangularwaveguides, the other waveguide orthomode transducer, the primaryradiator, the subreflector, and the main reflector over a large anglerange with respect to the direction of the azimuth angle withoutimpairing the electrical characteristics of the antenna apparatus ofthis embodiment. Therefore, the antenna apparatus can transmit thecircularly polarized wave signal while carrying out scanning of theantenna beam over a wide angle. It can be further expected that theantenna apparatus exhibits good passage and reflection characteristicsover a wide band.

Next, a case where the antenna apparatus receives a circularly polarizedwave signal C2 reflected from a target will be explained.

When receiving the circularly polarized wave signal C2, the mainreflector 16 reflects the circularly polarized wave signal C2 toward thesubreflector 15. The circularly polarized wave signal C2 is thenreflected by the subreflector 15 and is made to be incident upon theprimary radiator 14.

When receiving the circularly polarized wave signal C2, the primaryradiator 14 outputs the circularly polarized wave signal C2 to thewaveguide orthomode transducer 13.

When receiving the circularly polarized wave signal C2 outputted fromthe primary radiator 14 via the input/output terminal P9, the waveguideorthomode transducer 13 separates the circularly polarized wave signalC2 into linearly polarized wave signals L3 and L4, and then outputs thelinearly polarized wave signal L3 via the input/output terminal P7 andalso outputs the linearly polarized wave signal L4 having the sameamplitude as the linearly polarized wave signal L3 and having a phasedifference of 90 degrees with respect to the linearly polarized wavesignal L3 via the input/output terminal P8.

When receiving the linearly polarized wave signal L3 from theinput/output terminal P7 of the waveguide orthomode transducer 13, therectangular waveguide 10 a propagates the linearly polarized wave signalL3 to the rectangular waveguide 9 a, and the rectangular waveguide 9 athen propagates the linearly polarized wave signal L3 to the waveguideorthomode transducer 8.

On the other hand, when receiving the linearly polarized wave signal L4from the input/output terminal P8 of the waveguide orthomode transducer13, the rectangular waveguide 10 b propagates the linearly polarizedwave signal L4 to the rectangular waveguide 9 b, and the rectangularwaveguide 9 b then propagates the linearly polarized wave signal L4 tothe waveguide orthomode transducer 8.

When receiving the linearly polarized wave signal L3 propagated by therectangular waveguide 9 a via the input/output terminal P5 and alsoreceiving the linearly polarized wave signal L4 propagated by therectangular waveguide 9 b via the input/output terminal P6, thewaveguide orthomode transducer 8 combines the linearly polarized wavesignals L3 and L4 into a composite signal, and then outputs a circularlypolarized wave signal C1 which is the composite signal via theinput/output terminal P4.

When receiving the circularly polarized wave signal C1 from theinput/output terminal P4 of the waveguide orthomode transducer 8, therectangular-to-circular waveguide transformer 6 propagates thecircularly polarized wave signal C1 to the other rectangular-to-circularwaveguide transformer 4, and the other rectangular-to-circular waveguidetransformer 4 then propagates the circularly polarized wave signal C1propagated by the rectangular-to-circular waveguide transformer 6 to thewaveguide orthomode transducer 1.

When receiving the circularly polarized wave signal C1 propagated by therectangular-to-circular waveguide transformer 4 from the input/outputterminal P3, the waveguide orthomode transducer 1 separates thecircularly polarized wave signal C1 into linearly polarized wave signalsL1 and L2, and then outputs the linearly polarized wave signal L1 viathe input/output terminal P1 and also outputs the linearly polarizedwave signal L2 having the same amplitude as the linearly polarized wavesignal L1 and having a phase difference of 90 degrees with respect tothe linearly polarized wave signal L1 via the input/output terminal P2.

The antenna apparatus carries out reception of a circularly polarizedwave signal in this way. As in the case of transmission of a circularlypolarized wave signal, the antenna apparatus can drive the waveguideorthomode transducer, the rectangular waveguides, the other waveguideorthomode transducer, the primary radiator, the subreflector, and themain reflector over a wide angle range in both the direction of theelevation angle and the direction of the azimuth angle so as to receivea circularly polarized wave signal in good condition.

As shown in FIG. 2, the main reflector 16 is an antenna having arectangular aperture having a length “M” which is a size in thedirection of the elevation angle axis of rotation E and a length “W”(M>W) which is a size in a direction (referred to as a width directionfrom here on) perpendicular to the elevation angle axis of rotation E.The subreflector 15 is also an antenna having a rectangular aperturewhose size in the direction of the elevation angle axis of rotation E islarger than its size in the width direction.

The elevation angle axis of rotation E is made to pass through an almostcentral position of the distance (i.e., the height) H between the mainreflector and the subreflector in the direction (i.e., the heightdirection) of the azimuth axis of rotation D of the main reflector 16(refer to FIG. 1), and to pass through an almost central position of themain reflector 16 with respect to the width direction.

Therefore, when the main reflector 16 and the subreflector 15 arerotated around the elevation angle axis of rotation E, a movable area inwhich the main reflector 16 and the subreflector 15 can be moved existswithin a circle which is delineated by the outermost edge of the mainreflector 16, the circle having a center oh the elevation angle axis ofrotation E.

The movable area defined by this circle is very small as compared withthat provided by prior art antenna apparatus, and the profile of theantenna apparatus of this embodiment does not increase even if the mainreflector 16 and the subreflector 15 are made to rotate around theelevation angle axis of rotation E.

The main reflector 16 and the subreflector 15 are shaped, and receiveand reflect almost all of electromagnetic waves supplied thereto. Sincea concrete procedure for shaping the main reflector 16 and thesubreflector 15 is well known in this technical field, the detailedexplanation of the concrete procedure for shaping the main reflector 16and the subreflector 15 will be omitted hereafter. The procedure forshaping the main reflector and the subreflector is a technique forcontrolling the aperture shape and aperture distribution of an antenna,which is described in detail in, for example, IEE Proc. Microw. AntennasPropag. Vol. 146, No. 1, pp. 60 to 64, 1999.

In this embodiment, the main reflector and the subreflector are shapedso that the aperture of the antenna has a nearly rectangular shape andthe aperture distribution becomes uniform.

As can be seen from the above description, in accordance with thisembodiment 1, the rectangular waveguides 9 a and 10 a are formed so thatthey are bilateral symmetric to each other, the rectangular waveguides 9b and 10 b are formed so that they are bilateral symmetric to eachother, and the waveguide orthomode transducer 13 is disposed below thewaveguide orthomode transducer 8. Therefore, the present embodimentoffers an advantage of being able to reduce the profile of the antennaapparatus and to improve the installation stability without impairingthe electric characteristics of the antenna apparatus.

In other words, the present embodiment offers an advantage of being ableto achieve a downsizing and a low profile of the antenna apparatus byreducing the profile of the antenna apparatus. In addition, since theantenna apparatus has a bilateral symmetric structure, it excels inweight balance and offers stable performance from the viewpoint ofmechanism.

Embodiment 2

In above-mentioned embodiment 1, the rotation of the antenna apparatusaround the elevation angle axis of rotation E is implemented byinserting each of the rectangular waveguide rotary joints 11 a and 11 bbetween rectangular waveguides, as previously mentioned. As shown inFIG. 3, the rotation of the antenna apparatus around the elevation angleaxis of rotation E can be alternatively implemented by inserting each ofcoaxial-cable rotary joints 22 a and 22 b between rectangularwaveguides.

In other words, a coaxial-cable-to-rectangular-waveguide converter 21 ais connected to a rectangular waveguide 9 a and anothercoaxial-cable-to-rectangular-waveguide converter 23 a is connected to arectangular waveguide 10 a, and the coaxial-cable rotary joint 22 a isinserted between the coaxial-cable-to-rectangular-waveguide converter 21a and the other coaxial-cable-to-rectangular-waveguide converter 23 a.

In addition, a coaxial-cable-to-rectangular-waveguide converter 21 b isconnected to a rectangular waveguide 9 b and anothercoaxial-cable-to-rectangular-waveguide converter 23 b is connected to arectangular waveguide 10 b, and the coaxial-cable rotary joint 22 b isinserted between the coaxial-cable-to-rectangular-waveguide converter 21b and the other coaxial-cable-to-rectangular-waveguide converter 23 b.

Thus, the antenna apparatus according to this embodiment is partiallyconstructed of coaxial cables. Therefore, the present embodiment offersan advantage of being able to transmit and receive a good-qualitycircularly polarized wave signal in a further wide band withoutimpairing a downsizing and a low profile of the antenna apparatus, andwithout preventing wide angle scanning.

Embodiment 3

In either of above-mentioned embodiments 1 and 2, the internal structureof each of the waveguide orthomode transducers 1, 8, and 13 is notillustrated. Each of the waveguide orthomode transducers 1, 8, and 13can have an internal structure as shown in FIGS. 4 and 5. The waveguideorthomode transducers 1, 8, and 13 can have the same structure. For thesake of simplicity, FIGS. 4 and 5 show the structure of the waveguideorthomode transducer 8.

In FIGS. 4 and 5, when receiving a circularly polarized wave signal C1outputted thereto by a rectangular-to-circular waveguide transformer 6via an input/output terminal P4, a square main waveguide 31 transmitsthe circularly polarized wave signal (including a vertically polarizedelectric wave and a horizontally polarized electric wave) C1. Anothersquare main waveguide 32 has an aperture diameter larger than that ofthe square main waveguide 31 and a level difference at a connectingportion where it is connected to the square main waveguide 31, the leveldifference being sufficiently smaller than the free space wavelength ofan available frequency band. The other square main waveguide 32transmits the circularly polarized wave signal (including a verticallypolarized electric wave and a horizontally polarized electric wave) C1transmitted thereto by the square main waveguide 31.

A short-circuit plate 33 blocks one terminal of the square mainwaveguide 32, and a quadrangular-pyramid-shaped metallic block 34 isdisposed on the short-circuit plate 33 and separates the circularlypolarized wave signal into the vertically polarized electric wave andthe horizontally polarized electric wave. An electric wave branchingmeans comprises the square main waveguides 31 and 32, the short-circuitplate 33, and the quadrangular-pyramid-shaped metallic block 34.

Rectangular waveguide branching units 35 a to 35 d are connected to thesquare main waveguide 32 so that they are perpendicular to the fourwaveguide axes of the square main waveguide 32, respectively.Rectangular waveguide multi-stage transformers 36 a to 36 d areconnected to the rectangular waveguide branching units 35 a to 35 d,respectively, and have waveguide axes that are curved in an H plane andhave aperture diameters which decrease with distance from therectangular waveguide branching units 35 a to 35 d, respectively. Arectangular waveguide E-plane T-branching circuit 37 combines ahorizontally polarized electric wave transmitted by the rectangularwaveguide multi-stage transformer 36 a and a horizontally polarizedelectric wave transmitted by the rectangular waveguide multi-stagetransformer 36 b into a composite signal, and then outputs a linearlypolarized wave signal L3 which is the composite signal via theinput/output terminal P5. Another rectangular waveguide E-planeT-branching circuit 38 combines a vertically polarized electric wavetransmitted by the rectangular waveguide multi-stage transformer 36 cand a vertically polarized electric wave transmitted by the rectangularwaveguide multi-stage transformer 36 d into a composite signal, and thenoutputs a linearly polarized wave signal L4 which is the compositesignal via the input/output terminal P6.

A first electric wave propagating means comprises the rectangularwaveguide branching units 35 a and 35 b, the rectangular waveguidemulti-stage transformers 36 a and 36 b, and the rectangular waveguideE-plane T-branching circuit 37, and a second electric wave propagatingmeans comprises the rectangular waveguide branching units 35 c and 35 d,the rectangular waveguide multi-stage transformers 36 c and 36 d, andthe rectangular waveguide E-plane T-branching circuit 38.

Next, the operation of the waveguide orthomode transducer in accordancewith this embodiment of the present invention will be explained.

When the antenna apparatus receives a horizontally polarized electricwave H of basic mode (i.e., TE01 mode) via the input/output terminal P4,the square main waveguides 31 and 32 transmit the horizontally polarizedelectric wave H to the quadrangular-pyramid-shaped metallic block.

When the horizontally polarized electric wave H then reaches thequadrangular-pyramid-shaped metallic block 34, thequadrangular-pyramid-shaped metallic block causes it to branch towardboth the direction of the rectangular waveguide branching unit 35 a andthe direction of the rectangular waveguide branching unit 35 b (in thefigures, the directions of H: first horizontal symmetrical directions).

In other words, since each of the rectangular waveguide branching units35 c and 35 d has upper and lower walls having a gap which is equal toor smaller than one half of the free space wavelength of the availablefrequency band, the horizontally polarized electric wave H is not madeto branch toward the directions of the rectangular waveguide branchingunits 35 c and 35 d (in the figures, in the directions of V: secondhorizontal symmetrical directions) due to the interception effect of therectangular waveguide branching units 35 c and 35 d, but is made tobranch toward the directions of the rectangular waveguide branchingunits 35 a and 35 b (in the figures, in the directions of H).

Since the orientation of the electric field is changed along thequadrangular-pyramid-shaped metallic block 34 and the short-circuitplate 33, the electric field has a distribution equivalent to anelectric field distribution provided by two rectangular waveguideE-plane miter bends having excellent reflective characteristics whichare placed so that they are symmetric to each other. Therefore, thehorizontally polarized electric wave H is efficiently outputted in thedirections of the rectangular waveguide branching units 35 a and 35 bwhile leakage of the horizontally polarized electric wave H in thedirections of the rectangular waveguide branching units 35 c and 35 d issuppressed.

The level difference between the square main waveguides 31 and 32 at theconnecting portion where the square main waveguide 31 is connected tothe square main waveguide 32 is so designed as to be sufficiently smallas compared with the free space wavelength of the available frequencyband, and the connecting portion between the square main waveguides 31and 32 has reflection characteristics in which there is a largereflection loss in a frequency band near the cut-off frequency of thebasic mode of the horizontally polarized electric wave H and there is avery small reflection loss in a frequency band to some extent higherthan the cut-off frequency. The reflection characteristics are similarto the reflection characteristics of the above-mentioned branchingportion at which the horizontally polarized electric wave H is made tobranch toward the directions of the rectangular waveguide branchingunits 35 a and 35 b, and the above-mentioned connecting portion ispositioned so that a reflected wave from the branching portion and areflected wave from the above-mentioned connecting portion cancel eachother out in a band close to the cut-off frequency. Therefore, anydegradation in the reflection characteristics in the frequency band nearthe cut-off frequency can be suppressed without impairing the goodreflection characteristics in the frequency band to some extent higherthan the cut-off frequency of the basic mode of the horizontallypolarized electric wave H.

Each of the rectangular waveguide multi-stage transformers 36 a and 36 bhas a waveguide axis which is curved, and has an upper wall in which twoor more level differences are formed and the level differences arearranged at intervals of about one quarter of the wavelength of anelectric wave propagating therethrough with respect to a centerline ofthe waveguide. After all, the two components in the directions of therectangular waveguide branching units 35 a and 35 b toward which theelectric wave H is made to branch are combined into a composite wavesignal by the rectangular waveguide E-plane T-branching circuit 37 andthe composite wave signal is efficiently outputted via the input/outputterminal P5 without the reflection characteristics of the waveguideorthomode transducer being impaired.

On the other hand, when the waveguide orthomode transducer receives avertically polarized electric wave V of basic mode (i.e., TE10 mode) viathe input/output terminal P4, the square main waveguides 31 and 32transmit the vertically polarized electric wave V to thequadrangular-pyramid-shaped metallic block.

When the vertically polarized electric wave V then reaches thequadrangular-pyramid-shaped metallic block 34, thequadrangular-pyramid-shaped metallic block makes it branch toward both adirection of the rectangular waveguide branching unit 35 c and adirection of the rectangular waveguide branching unit 35 d (in thefigures, the directions of V).

In other words, since each of the rectangular waveguide branching units35 a and 35 b has upper and lower walls having a gap which is equal toor smaller than one half of the free space wavelength of the availablefrequency band, the vertically polarized electric wave V is not made tobranch toward the directions of the rectangular waveguide branchingunits 35 a and 35 b (in the figures, in the directions of H) due to theinterception effect of the rectangular waveguide branching units 35 aand 35 b, but is made to branch toward the directions of the rectangularwaveguide branching units 35 c and 35 d (in the figures, in thedirections of V).

Since the orientation of the electric field is changed along thequadrangular-pyramid-shaped metallic block 34 and the short-circuitplate 33, the electric field has a distribution equivalent to anelectric field distribution provided by two rectangular waveguideE-plane miter bends having excellent reflection characteristics whichare placed so that they are symmetric to each other. Therefore, thevertically polarized electric wave V is efficiently outputted in thedirections of the rectangular waveguide branching units 35 c and 35 dwhile leakage of the vertically polarized electric wave V in thedirections of the rectangular waveguide branching units 35 a and 35 b issuppressed.

The level difference between the square main waveguides 31 and 32 at theconnecting portion where the square main waveguide 31 is connected tothe square main waveguide 32 is so designed as to be sufficiently smallas compared with the free space wavelength of the available frequencyband, and the connecting portion between the square main waveguides 31and 32 has reflection characteristics in which there is a largereflection loss in a frequency band near the cut-off frequency of thebasic mode of the vertically polarized electric wave V and there is avery small reflection loss in a frequency band to some extent higherthan the cut-off frequency. The reflection characteristics are similarto the reflection characteristics of the above-mentioned branchingportion at which the vertically polarized electric wave V is made tobranch toward the directions of the rectangular waveguide branchingunits 35 c and 35 d, and the above-mentioned connecting portion ispositioned so that a reflected wave from the branching portion and areflected wave from the above-mentioned connecting portion cancel eachother out in a band close to the cut-off frequency. Therefore, anydegradation in the reflection characteristics in the frequency band nearthe cut-off frequency can be suppressed without impairing the goodreflection characteristics in the frequency band to some extent higherthan the cut-off frequency of the basic mode of the vertically polarizedelectric wave V.

Each of the rectangular waveguide multi-stage transformers 36 c and 36 dhas a waveguide axis which is curved, and has a lower wall in which twoor more level differences are formed and the level differences arearranged at intervals of about one quarter of the wavelength of anelectric wave propagating therethrough with respect to a centerline ofthe waveguide. After all, the two components in the directions of therectangular waveguide branching units 35 c and 35 d toward which theelectric wave V is separated made to branch are combined into acomposite wave signal by the rectangular waveguide E-plane T-branchingcircuit 38 and the composite wave signal is efficiently outputted viathe input/output terminal P6 without the reflection characteristics ofthe waveguide orthomode transducer being impaired.

Although the explanation of the principle of operation of the waveguideorthomode transducer is made as to the case where the input/outputterminal P4 is used as an input terminal and the input/output terminalsP5 and P6 are used as output terminals, the waveguide orthomodetransducer of this embodiment operates on the same principle ofoperation even in a case where the input/output terminals P5 and P6 areused as input terminals and the input/output terminal P4 is used as anoutput terminal.

As can be seen from the above description, this embodiment 3 offers anadvantage of being able to provide good reflection characteristics andisolation characteristics in a wide frequency band including a frequencyrange close to the cut-off frequency of the basic mode of the squaremain waveguide 32. Since the length of the square main waveguide 31 inthe direction of its waveguide axis can be shortened in each of thewaveguide orthomode transducers 1, 8, and 13, the physical size of theantenna apparatus can be reduced.

Embodiment 4

The antenna apparatus in accordance with above-mentioned embodiment 3uses the waveguide orthomode transducers 1, 8, and 13 each having astructure shown in FIGS. 4 and 5, as previously explained. As analternative, the antenna apparatus uses waveguide orthomode transducers1, 8, and 13 each having a structure shown in FIGS. 6 and 7. Thewaveguide orthomode transducers 1, 8, and 13 can have the samestructure. For the sake of simplicity, FIGS. 6 and 7 show the structureof the waveguide orthomode transducer 13.

In FIGS. 6 and 7, the same reference numerals as shown in FIGS. 4 and 5denote the same components or like components, and therefore theexplanation of these components will be omitted hereafter.

When receiving a circularly polarized wave signal C2 outputted theretofrom a primary radiator 14 via an input/output terminal P9, a circularmain waveguide 41 transmits the circularly polarized wave signal(including a vertically polarized electric wave and a horizontallypolarized electric wave) C2. Another square main waveguide 42 isconnected to the circular main waveguide 41, and has an aperturediameter larger than that of a square main waveguide 32 and a leveldifference at a connecting portion where it is connected to the squaremain waveguide 32, the level difference being sufficiently smaller thanthe free space wavelength of an available frequency band. The squaremain waveguide 42 transmits the circularly polarized wave signal(including a vertically polarized electric wave and a horizontallypolarized electric wave) C2 transmitted thereto by the square mainwaveguide 42.

When the antenna apparatus receives a horizontally polarized electricwave H of basic mode (i.e., TE01 mode) via the input/output terminal P9,the circular main waveguide 41 and the square main waveguides 42 and 32transmit the horizontally polarized electric wave H to aquadrangular-pyramid-shaped metallic block.

When the horizontally polarized electric wave H then reaches thequadrangular-pyramid-shaped metallic block 34, thequadrangular-pyramid-shaped metallic block makes it branch toward boththe direction of a rectangular waveguide branching unit 35 a and thedirection of a rectangular waveguide branching unit 35 b (in thefigures, in the directions of H).

In other words, since each of rectangular waveguide branching units 35 cand 35 d has upper and lower walls having a gap which is equal to orsmaller than one half of the free space wavelength of the availablefrequency band, the horizontally polarized electric wave H is not madeto branch toward the directions of the rectangular waveguide branchingunits 35 c and 35 d (in the figures, in the directions of V) due to theinterception effect of the rectangular waveguide branching units 35 cand 35 d, but is made to branch toward the directions of the rectangularwaveguide branching units 35 a and 35 b (in the figures, in thedirections of H).

Since the orientation of the electric field is changed along thequadrangular-pyramid-shaped metallic block 34 and a short-circuit plate33, the electric field has a distribution equivalent to an electricfield distribution provided by two rectangular waveguide E-plane miterbends having excellent reflective characteristics which are placed sothat they are symmetric to each other. Therefore, the horizontallypolarized electric wave H is efficiently outputted in the directions ofthe rectangular waveguide branching units 35 a and 35 b while leakage ofthe horizontally polarized electric wave H in the directions of therectangular waveguide branching units 35 c and 35 d is suppressed.

A connecting portion where the circular main waveguide 41 is connectedto the square main waveguide 42, the square main waveguide 42, and aconnecting portion where the square main waveguide 42 is connected tothe square main waveguide 32 serve as a circular-to-rectangularwaveguide multi-stage transformer. Therefore, when the diameter of thecircular main waveguide 41, the diameter of the square main waveguide 42and the length of the waveguide axis of the square main waveguide 42 areproperly designed, the circular-to-rectangular waveguide multi-stagetransformer has reflection characteristics in which there is a largereflection loss in a frequency band near the cut-off frequency of thebasic mode of the horizontally polarized electric wave H and there is avery small reflection loss in a frequency band to some extent higherthan the cut-off frequency. The reflection characteristics are similarto the reflection characteristics of the above-mentioned branchingportion at which the horizontally polarized electric wave H is made tobranch toward the directions of the rectangular waveguide branchingunits 35 a and 35 b, and the above-mentioned circular-to-rectangularwaveguide multi-stage transformer is positioned so that a reflected wavefrom the branching portion and a reflected wave from the above-mentionedcircular-to-rectangular waveguide multi-stage transformer cancel eachother out in a band close to the cut-off frequency. Therefore, anydegradation in the reflection characteristics in the frequency band nearthe cut-off frequency can be suppressed without impairing the goodreflection characteristics in the frequency band to some extent higherthan the cut-off frequency of the basic mode of the horizontallypolarized electric wave H.

Each of the rectangular waveguide multi-stage transformers 36 a and 36 bhas a waveguide axis which is curved, and has an upper wall in which twoor more level differences are formed and the level differences arearranged at intervals of about one quarter of the wavelength of anelectric wave propagating therethrough with respect to a centerline ofthe waveguide. After all, the two components in the directions of therectangular waveguide branching units 35 a and 35 b toward which theelectric wave H is made to branch toward are combined into a compositewave signal by a rectangular waveguide E-plane T-branching circuit 37and the composite wave signal is efficiently outputted via aninput/output terminal P7 without the reflection characteristics of thewaveguide orthomode transducer being impaired.

On the other hand, when the waveguide orthomode transducer receives avertically polarized electric wave V of basic mode (i.e., TE10 mode) viathe input/output terminal P9, the circular main waveguide 41 and thesquare main waveguides 42 and 32 transmit the vertically polarizedelectric wave V to the quadrangular-pyramid-shaped metallic block.

When the vertically polarized electric wave V then reaches thequadrangular-pyramid-shaped metallic block 34, thequadrangular-pyramid-shaped metallic block makes it branch toward both adirection of the rectangular waveguide branching unit 35 c and adirection of the rectangular waveguide branching unit 35 d (in thefigures, in the directions of V).

In other words, since each of the rectangular waveguide branching units35 a and 35 b has upper and lower walls having a gap which is equal toor smaller than one half of the free space wavelength of the availablefrequency band, the vertically polarized electric wave V is not made tobranch toward the directions of the rectangular waveguide branchingunits 35 a and 35 b (in the figures, in the directions of H) due to theinterception effect of the rectangular waveguide branching units 35 aand 35 b, but is made to branch toward the directions of the rectangularwaveguide branching units 35 c and 35 d (in the figures, in thedirections of V).

Since the orientation of the electric field is changed along thequadrangular-pyramid-shaped metallic block 34 and the short-circuitplate 33, the electric field has a distribution equivalent to anelectric field distribution provided by two rectangular waveguideE-plane miter bends having excellent reflection characteristics whichare placed so that they are symmetric to each other. Therefore, thevertically polarized electric wave V is efficiently outputted in thedirections of the rectangular waveguide branching units 35 c and 35 dwhile leakage of the vertically polarized electric wave V in thedirections of the rectangular waveguide branching units 35 a and 35 b issuppressed.

The connecting portion where the circular main waveguide 41 is connectedto the square main waveguide 42, the square main waveguide 42, and theconnecting portion where the square main waveguide 42 is connected tothe square main waveguide 32 serve as a circular-to-rectangularwaveguide multi-stage transformer. Therefore, when the diameter of thecircular main waveguide 41, the diameter of the square main waveguide 42and the length of the waveguide axis of the square main waveguide 42 areproperly designed, the circular-to-rectangular waveguide multi-stagetransformer has reflection characteristics in which there is a largereflection loss in a frequency band near the cut-off frequency of thebasic mode of the vertically polarized electric wave V and there is avery small reflection loss in a frequency band to some extent higherthan the cut-off frequency. The reflection characteristics are similarto the reflection characteristics of the above-mentioned branchingportion at which the vertically polarized electric wave V is made tobranch toward the directions of the rectangular waveguide branchingunits 35 c and 35 d, and the above-mentioned circular-to-rectangularwaveguide multi-stage transformer is positioned so that a reflected wavefrom the branching portion and a reflected wave from the above-mentionedcircular-to-rectangular waveguide multi-stage transformer cancel eachother out in a band close to the cut-off frequency. Therefore, anydegradation in the reflection characteristics in the frequency band nearthe cut-off frequency can be suppressed without impairing the goodreflection characteristics in the frequency band to some extent higherthan the cut-off frequency of the basic mode of the vertically polarizedelectric wave V.

Each of the rectangular waveguide multi-stage transformers 36 c and 36 dhas a waveguide axis which is curved, and has a lower wall in which twoor more level differences are formed and the level differences arearranged at intervals of about one quarter of the wavelength of anelectric wave propagating therethrough with respect to a centerline ofthe waveguide. After all, the two components in the directions of therectangular waveguide branching units 35 c and 35 d toward which theelectric wave V is made to branch are combined into a composite wavesignal by a rectangular waveguide E-plane T-branching circuit 38 and thecomposite wave signal is efficiently outputted via an input/outputterminal P6 without the reflection characteristics of the waveguideorthomode transducer being impaired.

Although the explanation of the principle of operation of the waveguideorthomode transducer is made as to the case where the input/outputterminal P9 is used as an input terminal and the input/output terminalsP7 and P8 are used as output terminals, the waveguide orthomodetransducer of this embodiment operates on the same principle ofoperation even in a case where the input/output terminals P7 and P8 areused as input terminals and the input/output terminal P9 is used as anoutput terminal.

As can be seen from the above description, this embodiment 4 offers anadvantage of being able to provide good reflection characteristics andisolation characteristics in a wide frequency band including a frequencyrange close to the cut-off frequency of the basic mode of the squaremain waveguide 32. Since the length of the square main waveguide 32 inthe direction of its waveguide axis can be shortened in each of thewaveguide orthomode transducers 1, 8, and 13, the physical size of theantenna apparatus can be reduced.

Embodiment 5

FIG. 8 is a side view showing an antenna apparatus according toembodiment 5 of the present invention, and FIG. 9 is a top plan viewshowing the antenna apparatus of FIG. 8.

In FIGS. 8 and 9, the same reference numerals as shown in FIGS. 1 and 2denote the same components as shown in the figures or like components,the explanation of these components will be omitted hereafter.

RF modules 51 a and 51 b are inserted into rectangular waveguides 10 aand 10 b, and amplify linearly polarized wave signals L3 and L4,respectively.

FIG. 10 is a block diagram showing the RF modules 51 a and 51 b, andeach of the RF modules 51 a and 51 b is provided with waveguidebranching filters 52 and 53 and a low noise amplifier 54.

Since the antenna apparatus according to this embodiment has the samestructure as that according to above-mentioned embodiment 1 with theexception that the RF modules 51 a and 51 b are inserted into therectangular waveguides 10 a and 10 b, respectively, only the operationof each of the RF modules 51 a and 51 b will be explained hereafter.

In accordance with above-mentioned embodiment 1, the rectangularwaveguides 9 a, 10 a, 9 b, and 10 b are routed so that the waveguideorthomode transducer 13 is disposed below the waveguide orthomodetransducer 8, and therefore the linearly polarized wave signals L3 andL4 outputted from the waveguide orthomode transducer 13 decrease inmagnitude with increase in the sizes of the rectangular waveguides 9 a,10 a, 9 b, and 10 b.

In contrast, in accordance with this embodiment 5, the RF modules 51 aand 51 b amplify linearly polarized wave signals L3 and L4 outputtedfrom the waveguide orthomode transducer 13, respectively, and also makelinearly polarized wave signals L3 and L4 outputted from the waveguideorthomode transducer 8 pass therethrough, just as they are,respectively.

In other words, the waveguide branching filter 52 of the RF module 51 abranches the linearly polarized wave signal L3 outputted from aninput/output terminal P7 of the waveguide orthomode transducer 13 towardthe low noise amplifier 54 without branching it toward the waveguidebranching filter 53. As a result, the low noise amplifier 54 amplifiesthe linearly polarized wave signal L3, and the waveguide branchingfilter 53 then outputs the amplified linearly polarized wave signal L3to an input/output terminal P5 of the waveguide orthomode transducer 8.

On the other hand, the waveguide branching filter 53 of the RF module 51a does not branch the linearly polarized wave signal L3 outputted fromthe input/output terminal P5 of the waveguide orthomode transducer 8toward the low noise amplifier 54, but branches it toward the waveguidebranching filter 52. The waveguide branching filter 52 then outputs thelinearly polarized wave signal L3 to the input/output terminal P7 of thewaveguide orthomode transducer 13.

Similarly, the waveguide branching filter 52 of the RF module 51 bbranches the linearly polarized wave signal L4 outputted from aninput/output terminal P8 of the waveguide orthomode transducer 13 towardthe low noise amplifier 54 without branching it toward the waveguidebranching filter 53. As a result, the low noise amplifier 54 amplifiesthe linearly polarized wave signal L4, and the waveguide branchingfilter 53 then outputs the amplified linearly polarized wave signal L4to an input/output terminal P6 of the waveguide orthomode transducer 8.

On the other hand, the waveguide branching filter 53 of the RF module 51b does not branch the linearly polarized wave signal L4 outputted fromthe input/output terminal P6 of the waveguide orthomode transducer 8toward the low noise amplifier 54, but branches it toward the waveguidebranching filter 52, and the waveguide branching filter 52 then outputsthe linearly polarized wave signal L4 to the input/output terminal P8 ofthe waveguide orthomode transducer 13.

This embodiment 5 offers an advantage of being able to suppressdegradation in quality due to a transmission loss of the linearlypolarized wave signals L3 and L4 caused by the rectangular waveguides 9a, 10 a, 9 b, and 10 b.

Embodiment 6

In accordance with above-mentioned embodiment 5, each of the RF modules51 a and 51 b is provided with the waveguide branching filters 52 and 53and the low noise amplifier 54. In contrast, in accordance with thisembodiment, the RF module 51 b can have a structure as shown in FIG. 11.The RF module 51 a can have the same structure as the RF module 51 b,though the RF module 51 a is not illustrated in the figure.

FIG. 11( a) is a cross-sectional view showing each of the RF modules 51a and 51 b, FIG. 11( b) is a side view of a single-sided corrugatedrectangular waveguide low pass filter 65 of FIG. 11( a) when viewed fromthe left side of the figure, FIG. 11( c) is a side view of asingle-sided corrugated rectangular waveguide low pass filter 66 of FIG.11( a) when viewed from the right side of the figure, FIG. 11( d) is aplan view of a low noise amplifier 71 and so on of FIG. 11( a) whenviewed from the upper side of the figure.

When a linearly polarized wave signal L4 outputted from an input/outputterminal P8 of a waveguide orthomode transducer 13, i.e., a basic mode(i.e., a rectangular waveguide TE01 mode) of an electric wave of a firstfrequency band is inputted to each RF module via an input/outputterminal P11, this electric wave propagates through a rectangular mainwaveguide 61, a stepped rectangular waveguide E-plane T-branchingcircuit 63, and the single-sided corrugated rectangular waveguide lowpass filter 65, and is then inputted into the low noise amplifier 71constructed of an MIC via a rectangular-waveguide-to-MIC converter 69.This electric wave is then amplified by the low noise amplifier 71.

The amplified electric wave is then outputted from anotherrectangular-waveguide-to-MIC converter 70, propagates through thesingle-sided corrugated rectangular waveguide low pass filter 66,another stepped rectangular waveguide E-plane T-branching circuit 64,and a rectangular main waveguide 62, and is outputted, as the basic modeof the rectangular waveguide, to an input/output terminal P6 of awaveguide orthomode transducer 8 via an input/output terminal P12.

On the other hand, when a linearly polarized wave signal L4 outputtedfrom the input/output terminal P6 of the waveguide orthomode transducer8, i.e., a basic mode (i.e., a rectangular waveguide TE01 mode) of anelectric wave of a second frequency band higher than the first frequencyband is inputted to each RF module via the input/output terminal P12,this electric wave propagates through the rectangular main waveguide 62,the stepped rectangular waveguide E-plane T-branching circuit 64,inductive iris coupled rectangular waveguide band pass filters 68 and67, the stepped rectangular waveguide E-plane T-branching circuit 63,and the rectangular main waveguide 61, and is outputted, as the basicmode of the rectangular waveguide, to the input/output terminal P8 ofthe waveguide orthomode transducer 13 via the input/output terminal P11.

Each of the single-sided corrugated rectangular waveguide low passfilters 65 and 66 is so designed as to allow any electric wave of thefirst frequency band to pass therethrough and to reflect any electricwave of the second frequency band. In contrast, each of the inductiveiris coupled rectangular waveguide band pass filters 67 and 68 is sodesigned as to allow any electric wave of the second frequency band topass therethrough and to reflect any electric wave of the firstfrequency band.

In addition, the stepped rectangular waveguide E-plane T-branchingcircuit 63 has a matching step that is disposed at a branching portionthereof and is designed so that both a reflected wave caused therebywhen an electric wave of the first frequency band is incident thereuponfrom the rectangular main waveguide 61, and a reflected wave causedthereby when an electric wave of the second frequency band is incidentthereupon from the inductive iris coupled rectangular waveguide bandpass filter 67 are reduced as much as possible, respectively.

Similarly, the stepped rectangular waveguide E-plane T-branching circuit64 has a matching step that is disposed at a branching portion thereofand is designed so that both a reflected wave caused thereby when anelectric wave of the first frequency band is incident thereupon from thesingle-sided corrugated rectangular waveguide low pass filter 66, and areflected wave caused thereby when an electric wave of the secondfrequency band is incident thereupon from the rectangular main waveguide62 are reduced as much as possible, respectively.

As a result, the electric wave of the first frequency band inputted toeach RF module via the input/output terminal P11 is efficiently inputtedinto the low noise amplifier 71 while both reflection of the electricwave to the input/output terminal P11, and direct leakage of theelectric wave to the stepped rectangular waveguide E-plane T-branchingcircuit 64 are suppressed. Furthermore, the electric wave of the firstfrequency band amplified by the low noise amplifier 71 is efficientlyoutputted via the input/output terminal P12 without being sent back tothe stepped rectangular waveguide E-plane T-branching circuit 63.

In addition, the electric wave of the second frequency band inputted toeach RF module via the input/output terminal P11 is efficientlyoutputted via the input/output terminal P11 while both reflection of theelectric wave to the input/output terminal P12 and leakage of theelectric wave to the low noise amplifier 71 are suppressed.

According to this embodiment 6, at the same time that each RF moduleefficiently amplifies and makes an electric wave of the first frequencyband inputted thereto via the input/output terminal P11 passtherethrough without making the electric wave oscillate, each RF modulecan make most of an electric wave of the second frequency band inputtedthereto via the input/output terminal P12 pass therethrough with almostno loss of the electric wave. In addition, when the number of resonatorsincluded in each of the inductive iris coupled rectangular waveguideband pass filters 67 and 68 is properly reduced, the distance betweenthe input/output terminal P11 to the input/output terminal P12 isshortened. In this case, the physical size and weight of each RF modulecan be reduced and the performance of each RF module can be enhanced.

Embodiment 7

In the antenna apparatus according to either of above-mentionedembodiments 1 to 6, a linearly polarized wave signal L1 is outputted orinputted via the input/output terminal P1 of the waveguide orthomodetransducer 1, and a linearly polarized wave signal L2 is outputted andinputted via the input/output terminal P2, as previously mentioned. Incontrast, an antenna apparatus according to this embodiment is providedwith an input/output means for outputting or inputting a linearlypolarized wave signal L1 via an input/output terminal P1 of a waveguideorthomode transducer 1, and for outputting or inputting a linearlypolarized wave signal L2 via an input/output terminal P2 of thewaveguide orthomode transducer 1, as shown in FIG. 12.

In this embodiment, the input/output means comprises waveguide branchingfilters 81 and 82, a waveguide 90-degree hybrid circuit 83, acoaxial-cable 90-degree hybrid circuit 84, high power amplifiers 85 and86, low noise amplifiers 87 and 88, variable phase shifters 89 to 92,coaxial-cable 90-degree hybrid circuits 93 and 94, andcoaxial-cable-to-waveguide converters 95 and 96.

Thus, by using the input/output means, the antenna apparatus can receivea right-hand circularly polarized wave signal and a left-hand circularlypolarized wave signal, and can also transmit and receive a linearlypolarized wave having an arbitrary angle.

INDUSTRIAL APPLICABILITY

As mentioned above, the antenna apparatus in accordance with the presentinvention can be used in a VHF band, a UHF band, a microwave band, amillimeter wave band, etc.

1. An antenna apparatus comprising: a first orthomode transducer forcombining first and second linearly polarized wave signals into acircularly polarized wave signal and for outputting the circularlypolarized wave signal; a second orthomode transducer disposed above saidfirst orthomode transducer, for separating the circularly polarized wavesignal outputted thereto from said first orthomode transducer into thirdand fourth linearly polarized wave signals, and for outputting them; afirst rectangular waveguide for propagating the third linearly polarizedwave signal outputted thereto from said second orthomode transducer; asecond rectangular waveguide disposed bilateral symmetrically to saidfirst rectangular waveguide, for propagating the fourth linearlypolarized wave signal outputted thereto from said second orthomodetransducer; a third orthomode transducer disposed below said secondorthomode transducer, for combining the third and fourth linearlypolarized wave signals respectively propagated thereto by said first andthe second rectangular waveguides into a circularly polarized wavesignal, and for outputting the circularly polarized wave signal; and aradiator disposed above said third orthomode transducer, for emittingthe circularly polarized wave signal outputted thereto from said thirdorthomode transducer to a reflector.
 2. The antenna apparatus accordingto claim 1, characterized in that when said radiator receives acircularly polarized wave signal from said reflector, said thirdorthomode transducer separates the circularly polarized wave signal intothird and fourth linearly polarized wave signals and outputs them, and,when receiving third and fourth linearly polarized wave signals from thefirst and the second rectangular waveguides, respectively, said secondorthomode transducer combines said third and fourth linearly polarizedwave signals into a circularly polarized wave signal, and outputs it,and said first orthomode transducer separates the circularly polarizedwave signal into first and second linearly polarized wave signals andoutputs them.
 3. The antenna apparatus according to claim 2,characterized in that an elevation angle rotary member for supportingrotation of said radiator and said reflector in a direction of anelevation angle is inserted into each of said first and secondrectangular waveguides.
 4. The antenna apparatus according to claim 3,characterized in that an azimuth rotary member for supporting rotationof said radiator and said reflector in a direction of an azimuth angleis inserted between said first orthomode transducer and said secondorthomode transducer.
 5. The antenna apparatus according to claim 3,characterized in that said elevation angle rotary member is constructedusing a coaxial-cable rotary joint.
 6. The antenna apparatus accordingto claim 1, characterized in that each of said orthomode transducerscomprises an electric wave branching means for, when receiving acircularly polarized wave signal, making a horizontally polarizedelectric wave included in the input circularly polarized wave signalbranch toward first horizontal symmetrical directions, and making avertically polarized electric wave included in the circularly polarizedwave signal branch toward second horizontal symmetrical directions, afirst electric wave propagating means for propagating a part of thehorizontally polarized electric wave and a remaining part of thehorizontally polarized electric wave branched by said electric wavebranching means, for combining both the parts of the horizontallypolarized electric wave into a linearly polarized wave signal, and foroutputting it, and a second electric wave propagating means forpropagating a part of the vertically polarized electric wave and aremaining part of the vertically polarized electric wave branched bysaid electric wave branching means, for combining both the parts of thevertically polarized electric wave into a linearly polarized wavesignal, and for outputting it.
 7. The antenna apparatus according toclaim 2, characterized in that an RF module for amplifying a linearlypolarized wave signal inputted thereto is inserted into each of saidfirst and second rectangular waveguides.
 8. The antenna apparatusaccording to claim 7, characterized in that said RF module comprises anamplification path for amplifying the linearly polarized wave signaloutputted from said third orthomode transducer and for outputting theamplified, linearly polarized wave signal to said second orthomodetransducer, and a passage path for outputting the linearly polarizedwave signal outputted from said second orthomode transducer to saidthird orthomode transducer.
 9. The antenna apparatus according to claim2, characterized in that said apparatus is provided with an input/outputmeans for inputting and outputting the first and second linearlypolarized wave signals to and from the first orthomode transducer. 10.The antenna apparatus according to claim 3, characterized in that saidreflector has a rectangular aperture having a larger size in a directionof an elevation angle axis than a size in a direction perpendicular tothe elevation angle axis.